Australia’s Bureau of Meteorology (BOM) recently predicted the occurrence of a third consecutive event of La Nina, possibly leading to unusual weather effects in various countries. This exceptional period of La Nina in 2022 is the first of its kind since the 1950s when these events started to be recorded. Past consecutive La Nina years had been observed in 1973-76 and 1998-2001.
Characteristics and Effects of La Nina
La Nina, Spanish for ‘The Little Girl’, refers to periods of below-average sea surface temperatures across the east-central Equatorial Pacific. The phenomenon is indicated by a more than 0.9℉ decrease in sea-surface temperature for at least five successive three-month seasons.
In Europe, La Nina can lead to milder winters in Northern Europe and colder winters in southern/western Europe, occasionally causing snowfall in the Mediterranean region. Continental North America experiences most of these conditions, including stronger winds along the equatorial region, favorable conditions for hurricanes in the Caribbean and central Atlantic area, and greater instances of tornadoes in various parts of the US. In South America, La Nina causes drought in Peru and Ecuador, yet often positively impacts the western South American fishing industry. The western Pacific sees an increase in landfall potential in vulnerable areas, particularly continental Asia and China, and heavy floods in Australia.
El Nino: The Warm Counterpart
In contrast to La Nina, El Nino is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean. This “warm phase” occurs more frequently than La Nina.
El Nino impacts not only ocean temperatures, speed, and strength of currents, but also coastal fisheries health and local weather from Australia to South America and beyond. Increased precipitation in South America due to convection above warmer surface waters often results in coastal flooding and erosion. Additionally, diseases such as cholera, dengue, and malaria thrive in communities affected by natural hazards like floods or droughts. However, El Nino can have positive impacts, such as reducing hurricane instances in the Atlantic.
India’s Anticipation of Third Consecutive La Nina
The India Meteorological Department (IMD) recently reported that La Nina conditions currently prevail over the equatorial Pacific Ocean. Some parts of India may witness heavy rains while the Western Ghats may receive average or below-average rain. North India will experience less than normal winter rainfall, snowfall over the Western Himalayas, lower winter temperatures in the plains, and a prolonged winter season. The second half of the Northeast Monsoon may bring more rain.
Agricultural Implications of Continuous La Nina Events
Continued La Nina conditions may risk the loss of standing Kharif crops if untimely rains coincide with the harvest. The harvest generally begins in late September or early October. Therefore, rain around this time would be detrimental to standing crops, causing a double whammy for farmers.
Conceptualizing the Indian Ocean Dipole (IOD)
The Indian Ocean Dipole (IOD) is an atmosphere-ocean coupled phenomenon in the tropical Indian Ocean. It is characterized by a difference in Sea-Surface Temperatures (SST). A ‘positive IOD’ is associated with cooler than normal sea-surface temperatures in the eastern equatorial Indian Ocean and warmer than normal sea-surface temperatures in the western tropical Indian Ocean. The reverse, a ‘negative IOD’, is characterized by warmer than normal SSTs in the eastern equatorial Indian Ocean and cooler than normal SSTs in the western tropical Indian Ocean. Also known as the Indian Nino, it is an irregular oscillation of sea-surface temperatures in the Indian Ocean.
Coping with El Nino and La Nina Fallout in India
In view of the 2010 guidelines from the National Disaster Management Authority (NDMA), mechanisms have been proposed for preparedness to deal with likely El Nino and La Nina fallouts in India. These include developing a comprehensive strategy for drought management, strengthening drought monitoring and forecasting, crop diversification, rainwater harvesting, and watershed development.